Wastewater worries

Columbia’s wastewater plant is four years overdue for an upgrade, and the price tag for the necessary expansion could be $90 million.
Wednesday, June 13, 2007 | 12:00 a.m. CDT; updated 2:50 p.m. CDT, Thursday, July 17, 2008
Joel Gambill, plant superintendent at the City of Columbia Wastewater Treatment Plant, watches aeration basins at work. Gambill may have a larger plant to oversee if voters pass a $65 million plan to expand the city’s sewer system, which could be on the ballot as early as April.

Every time a Columbia resident flushes his or her toilet, the contents flow past Joel Gambill’s office window.

Columbia’s sewage treatment plant sees, on average, about 16 million gallons of toilet water, sink scum and storm runoff each day. Gambill’s job is to oversee operations to remove harmful solids and chemicals before water is pumped into the city wetlands for further treatment.

How it works

The city wastewater treatment plant on Gillespie Bridge Road consists of a wastewater pump building and two sets of basins that treat the effluent. The sets of basins, called “trains,” are made up of two settling basins, which separate solids from water, and an aeration basin that introduces oxygen and microorganisms that consume harmful bacteria. Raw sewage is first pumped in from the city’s sewer systems through the pumping building into the first settling basin. After small particles have been separated out, the water is transferred to the aeration basin, where large wheels spin the water rapidly, letting in air. Next, the water moves into the final settling basin, where any remaining solids, or sludge, are removed. The treated effluent is piped downstream to the last stage of the treatment process, on 130 acres of constructed wetland treatment cells located south of Columbia in the Missouri River bottoms near McBaine. The treated wastewater flows into the wetlands, where cattails consume harmful nutrients.

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Gambill said the treatment plant is meeting clean water standards, but population growth is creating demand that will soon be too much for the 25-year-old facility to handle.

“The plant’s at capacity, the town is growing, and the amount of wastewater coming to the plant is increasing,” said Steve Hunt, a civil engineer with the city’s Public Works Department.

The plant, which was designed in 1983 to last 20 years, is due for an upgrade, something that was discussed at the annual City Council retreat last weekend.

“Right now we’re at capacity, and we’ve got do something about it,” City Manager Bill Watkins told council members on Friday.

A $65 million plan to revamp the city’s sewer system is expected to go to voters as early as April. The city also plans to ask voters next year to approve a separate $44.5 million bond issue for the city’s drinking water system.

An estimated $44 million of the sewer bonds would go toward updating the treatment system; the balance would finance the sewer collection system.

“Forty-four million is a huge number, but we’ve known this was coming,” Watkins said.

The $65 million in bonds would pay for the first phase of an expansion that Hunt said would eventually total $90 million.

The expansion would increase the amount of wastewater treated daily from the current average of 16 million gallons to 26 million gallons during the first phase of the expansion. Hunt said the goal is to eventually increase that average to 32 million gallons, with the capacity to treat a maximum of 60 million gallons. The existing facility can handle up to 20.6 million gallons per day.

A presentation at the council retreat by Public Works Director John Glascock showed sewer rate increases through 2012 to pay for the bonds, with the highest increase in 2008. Rates are expected to stay below $20 per month.

The current average sewer utility bill is $11.50 per month and is based on water consumption. Columbia’s sewer utility is paid for entirely though sewer bills.

The City Council is expected to vote Monday on an agreement with Black & Veatch, an engineering and consulting firm, on a conceptual design for expansion of treatment facilities.

The agreement with Black & Veatch is for a study to determine how to implement the expansion plan recommended in the Wastewater Facilities Master Plan approved by the City Council in 2004.

Black & Veatch will keep in mind future wastewater loads, as well as future government regulation of water pollutants, including nitrogen and phosphorous removal, Hunt said.

Black & Veatch will also evaluate the city’s treatment wetlands to see whether any improvements can be made. The wetlands are designed to handle 60 million gallons of water per day and are not in line for expansion.

“The additions to the facility will make it more cost-effective and produce a higher quality effluent,” Gambill said. “The cleaner the water is that comes out of the plant, the better the wetlands will be able to do their job.”

If the council on Monday approves the engineering work, consultants will begin by the end of June. Public Works is aiming to begin construction in 2010.

Missourian reporter Jewels Phraner contributed to this report.

A portion of this report first aired Tuesday during “News At 10” on KMIZ/Channel 17 ABC, Columbia.

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